Plastering over inside wall treated with Thompsons WaterSeal

[meanwhileinhell]

Hi,

I have a damp problem in my dining room. I was seeing large patches on the wall appear when there was rain. I was told by a damp specialist to remove the plaster to the brick, repoint the brick, apply a water proofer and replaster the wall. I have done the stripping, and repointing, and used Thompsons Water Seal as the damp proofer. I used this after asking a member of staff in the building supply store what I would need and explained what I was doing and they pointed me to it.

However, I have recently got the same damp specialist back to install a DPC and he has told me that the Thompsons Water Seal is only to be used on the outside walls, and that when it comes to replastering the wall, it will be a nightmare as the plaster will not stick correctly due to the water not taking to the brick. He said that he will supply me with the correct type of water proofer when he arrives to do the DPC.

Will this be a major problem? What will I need to do to the wall in order to remove the Thompsons Water Seal so that the correct water proofer takes to the wall?? Will replastering be tough?

Thanks.

 

[stevethespreader]

first time ive come across this, you must have asked the local numty in the store,
anyway i dont think you will be able to remove the waterseal as from what i understand it penitrates quite deep, i think the solution would be to spatterdash the walls to povide a key before the wall is rendered if your using sand and cement, an alternative would be to use bonding because you have sealed the walls up making them low or none suction, but i would prefer the splatterdash and sand and cement if it was my house

 

[peaps]

I would take a good scutch chisel to the brickwork.

 

[meanwhileinhell]

Thanks for the replies. How would I apply a splatterdash to the wall?

If I went for the bonding option, what would you use for this? Is this applied to the wall before applying a sand and cement render?

The damp specialist arrived today and gave me a packet of the correct water proofer, said to mix it with the water used in the render.

 

[stevethespreader]

Thanks for the replies. How would I apply a splatterdash to the wall?

If I went for the bonding option, what would you use for this? Is this applied to the wall before applying a sand and cement render?

The damp specialist arrived today and gave me a packet of the correct water proofer, said to mix it with the water used in the render.

forget about the bonding its an undercoat for low suction backgrounds which could have been an option but go with the render heres a link to a guide using sbr its good for low suction walls which you now have because of the water seal http://www.permagard.co.uk/media/uploads/SBR Bonding Additive Data Sheet.pdf , or you could just spatterdash with cement or cement with a hand full of sand which would still give you a mechanical key

 

[peaps]

If you are going to use the addertive then you don't need to use SBR. SBR is a good product by the way but it is latex based and if you add more cemicals to it it will/may change it's structure and performance.

 

[meanwhileinhell]

Ok, so going to go with the spatterdash. Will just using sand and cement be enough, or will I need to add an additive (like the SBR)?

Also, what is the best technique to apply the spatterdash? Is there a tool for it or is it simply throwing some s+c hard against the wall?

 

[Micilin]

SBR is designed to be used with cement or sand and cement as steve suggests.

You could also paint with blackjack and blind it by throwing sharp sand into the wet black jack. When dry, render onto this as the sand gives a key

 

[stevethespreader]

Ok, so going to go with the spatterdash. Will just using sand and cement be enough, or will I need to add an additive (like the SBR)?

Also, what is the best technique to apply the spatterdash? Is there a tool for it or is it simply throwing some s+c hard against the wall?

sbr will give the spatterdash bonding qualities its not always needed, apply spatterdash with a brush

 

[northernwarrior]

to be honest i don't think using sbr and cement as a "spatterdash" will help you out of this situation, as far as i am aware Thompsons is silicone suspended in a solvent, so this will repel any thing that you apply that is water based, either create a really good mechanical key (grind out all mortar joints and score the bricks heavily, as suggested previously) or fix an oldroyed type membrane with mechanical fixings and then render or plaster in dri coat etc

 

[Micilin]

The SBR slurry /scud will stick, blackjack will stick. As there is a seal there already, is there any need to break it?

 

[peaps]

to be honest i don't think using sbr and cement as a "spatterdash" will help you out of this situation, as far as i am aware Thompsons is silicone suspended in a solvent, so this will repel any thing that you apply that is water based, either create a really good mechanical key (grind out all mortar joints and score the bricks heavily, as suggested previously) or fix an oldroyed type membrane with mechanical fixings and then render or plaster in dri coat etc

Yes do it right I say.

 

[Micilin]

SBR slury is not water based.

Why remove/degrade a water repellent coat in an area that may have damp?

 

[northernwarrior]

SBR slury is not water based.

Why remove/degrade a water repellent coat in an area that may have damp?

Don't know where you get your SBR from but mine is definitely diluted in water, at the end of the day the wrong product was used , and yes there is a barrier there but nothing will stick to it!!, fix a membrane over it and save your self some trouble

 

[joe-90]

Your damp proofer is talking bollux anyway. a house gets barely any water on the walls when it rains. To make the walls wet it is coming off your roof somehow.